1. Field of the Invention
The present invention relates to a method of manufacturing a thin film device, and more particularly, to a method of manufacturing a thin film device using a thin film transfer process that can be used as a technique for manufacturing a flexible substrate.
2. Description of the Related Art
In general, a thin-film transfer technique has been widely used in thin film devices, such as thin film transistors (TFTs), electronic devices, and optical devices including organic EL devices.
The thin-film transfer technique generally refers to a technique that forms a predetermined thin film on a preliminary substrate and then transfers the thin film onto a permanent substrate to thereby manufacture a desired thin film device. This thin-film transfer technique can be of great use when conditions of a substrate used to form a film are different from those of a substrate used in a thin film device.
For example, even though a semiconductor thin-film forming technique requires a relatively high-temperature process, if a substrate used in a thin film device has low thermal resistance or a low softening point and a low melting point, the thin-film transfer technique can be very advantageously applied. Particularly, the thin-film transfer technique can be advantageously applied to flexible thin-film devices.
In the related art, since a flexible device needs to have flexibility, an organic substrate formed of, such as a polymer, is used, and an organic thin film serving as a functional unit is disposed on the top of the organic substrate. However, since it is difficult to ensure high performance by the functional unit formed of the organic thin film, an inorganic material, such as polysilicon (poly-Si) or an oxide thin film, is used to form a functional unit of the flexible device. Here, since it is difficult to directly apply the high-temperature semiconductor film forming technique to the flexible substrate formed of the organic material, the thin-film transfer technique that transfers a thin film formed of an inorganic material, such as a semiconductor, onto another preliminary substrate is used.
However, a surface that is separated from the preliminary substrate is provided as an upper surface of the thin film transferred onto the permanent substrate, and remnants of a sacrificial layer remain on the upper surface. Therefore, a process of removing the remnants of the sacrificial layer is further required in order to prevent it having an adverse effect on the thin film device.
When a thin film pattern is required, a patterning process is generally performed after transferring the thin film onto the permanent substrate. If the patterning process has been previously performed, the permanent substrate, used as a support substrate, may be damaged by laser irradiation when removing the sacrificial layer in order to separate the permanent substrate from the preliminary substrate.
However, when the patterning process is performed after the thin film has been transferred onto the permanent substrate, thermal-chemical damage to the permanent substrate caused by the patterning process needs to be considered.